The present invention relates to a coil device used as a solenoid.
In a conventional coil device such as disclosed in Japanese utility model publication No. Hei3(1991)-33046 published after examination, each of the ends of a wire wound around a resin bobbin is connected to a terminal corresponding thereto, and a resin protective layer is provided on parts of the wire and the terminals. When such a coil device is incorporated in a specific apparatus such as a solenoid, those parts are subjected to a concentration of stress if there is a big change in the ambient temperature because of the shrinkage force acting between the ends of the wire and the respective terminals. In this case, there will be no problem if the size of the wire is large enough. However, it is sometimes inevitable that a wire having a small diameter is used in view of the rating of the coil device. In such a case, since there is a possibility of wire disconnection due to the concentration of stress, it is necessary to wind wire with a tension which is somewhat small.
Such approach, however, can result in improper winding, creating a problem that the inductance of the coil can derive from the design value.